Apparatus for treating pulp with liquid



Jan. 17, 1956 Filed Dec. 31, 1952 G. A. SEELY ETAL APPARATUS FORTREATING PULP WITH LIQUID 2 Sheets-$heet 1 GEORGE A.SEELY WALTER E. SEGLERNEST 8. WILSON INVENTORS Jan. 17, 1956 s. A. SEELY ETI'AL APPARATUSFOR TREATING PULP WITH LIQUID 2 Sheets-Sheet 2 Filed Dec. 51. 1952 FIG 3FIG. 4

GEORGE A. SEELY WALTER E. SEGL ERNEST 8. WILSON INVENTOR.

AGENT.

United States Patent APPARATUS FOR TREATKNG PULP WIT H LIQUID George A.Seely, Hopewell, Va., and Walter E. Segl and Ernest S. Wilson,Wilmington, DeL, assignors to Her.- cules Powder Company, Wilmington,Del a corporw tion of Delaware Application December 31, 1952, Serial No.329,074

Claims. (Cl. 68-181) This invention relates to an improved pulptreatment apparatus. In a specific aspect, this invention relates to animproved high density tower for the continuous treat me 4r P lp- In thebleaching of pulp, it has sometimes been found desirable to employ inthe process a high density bleach tower wherein pulp to be bleached iscontinuously fed to the top of the tower and bleached pulp iscontinuously removed from the base of the tower. The bleached pulp iswashed with water and the washed pulp is then ready for furthertreatment. The pulp entering the top of the tower is usually hot andwetted with bleach solution. The pulp contains sufficient bleachsolution for the bleaching reaction, but there is susbtantially no freebleach solution present in the entering feed stock. As the mass of pulppasses downwardly through the bleach tower, the compressive force of thepulp in the upper portion of the bleach tower tends to form a hard,compact mass in alower portion of the tower. It is thus apparent thatthe removal of the bleached pulp from the base of the bleach tower canbe a difficult operation.

One of the prior art methods of removing bleached pulp from the base ofthe tower involved the use of a revolving scraper to keep the bleachedpulp flowing through a discharge opening in the bottom of the tower.Since the pulp is in a hard, compact mass in the bottom of the tower,the difiiculty of employing such an apparatus is quite apparent. Anotherprior art method involved the insertion of a pylon in the bottom of thetower and a water spray was employed to slurry and to regulate theremoval of the bleached pulp. This method contemplatedthat the stockwould bridge from the pylon to the tower wall and that the downwardpassage of the stock could then be regulated by the water spray.However, the stool: frequently would not bridge and withdrawal of thebleached pulp was quite difiicult and uncontrollable.

It is an object of this invention to provide a novel and improved bleachtower.

It is another object of this invention to provide a novel and improvedtower for the bleaching of pulp wherein the construction of the towerpermits uniform and controllable removal of the bleached pulp in aliquid slurry.

Further andadditional objects of this invention will be apparent fromthe detailed disclosure and the accompanying drawing. a

The apparatus of this invention comprises an elongated, verticallydisposed chamber or tower for bleaching pulp containing a cellulosicmaterial, such as cotton lin ters or wood pulp. The bottom portion ofthe tower is provided with a bulged or protuberant section, and disposed within this protubcrant section are a solid, circular bathe eitherhorizontally disposed or sloping downwardly from the center of thechamber to the wall of the chamber, and means for moving or forcingbleached pulp toward the wall of the chamber.

Fig. 1 is an elevational view of the improved bleaching tower.

2,730,888 Patented Jan. 17, 1956 Fig. 2 is a plan view through section2--2 of the improved bleaching tower.

Figs. 3 and 4 are alternative elevational views of the improvedbleaching tower.

Referring now to the accompanying drawings, Figs. 1, 3 and 4 areelevational views of the improved bleaching tower of this invention.Bleaching tower or column 10 is an elongated cylindrically shapedchamber containing bleaching zone 10a and a slurrying zone 10b. In mostinstances, the bleaching zone which is in the upper portion of thecolumn comprises the major portion, for example, about or more of theentire volume of the column. However, it will be understood that thevolumetric proportions of the bleaching Zone and slurrying zone arevariable and depend upon such factors as the material being processed,treatment time, and the like. The bleaching zone and slurrying zone ofcolumn 10 are separated by a bulged or protuberant section 12 of thebleach tower. A desirable design for this bulged section of the columnis an enlarged cylindrical section superimposed upon and in directcommunication with an inverted truncated cone. The inverted truncatedcone tapers downwardly and inwardly toward the lower portion of thecolumn or the slurrying zone, and the enlarged cylindrical section islarger in diameter than the diameter of the bleaching zone of thecolumn. A solid circular battle or umbrella 14 is disposed in thecylindrical portion of bulged section 12. Baflle 14 preferably slopesdownwardly from the center of the column toward the outer wall of thebulged section, but, if desired, a horizontally disposed baffle can beused. The lower or outer extremity of battle 14 is in the bulged sectionof the column. Thus, the radius of baflle 14 is greater than the radiusof the bleaching zone of column 10 and baffle 14 forms an annular spacewith the outer wall of the cylindrical portion of bulged section 12.Also, disposed within bulged section 12-and above baffle 14 aretransport jets l6 and slice arms 18 which provide a means fordisintegrating any remaining piers or pillars of pulp that tend to formin the bleaching section of column 10. The action of jets 16 andslicearms 18 forces or moves the pulp around baffle M and into the slurryingsection of column 10. Jets 16 and slice arms 18 are attached to andsupported by revolving nozzle block 34 which is disposed above pylon 20.Supporting ribs 36 attached to baflle 14 and pylon 20 provide thenecessary support for baffle 14. Pylon 20 forms a casing through whichWater or other fluid is forced for passage through jets 16. Jets 16 andslice arms 18 are revolved by power shaft 22 which is at: tached to asource of power not shown. Zone 1% is provided with agitating means 38to maintain the slurry consistency in zone 1013.

There are other designs for column '10 which incorpoi-ate this inventionand which are within the scope of the invention. For example, the lowerportion of the column, which includes the bulged section and theslurryin zone, can be of substantially uniform diameter, as shown inFig. 3. In that event the diameter of the entire lower portion of thecolumn will be greater than the diameter of the bleaching zone of thecolumn. desired, the diameter of the slurrying zone of the column can besmaller than the diameter of the bleaching Zone, as shown in Fig. 4. Theimportant feature is theprovision of a zone between the bleaching andslurrying zones of greater diameter than the bleaching zone and housingbaffle 14, jets 16 and arms 18. The optimum radius of arms 18 issubstantially as great as the radius of the bleaching zone of column 10in order to. insure com plete disintegration of any piers of bleachedlinters that are formed. The radius of arm 18 can be greater than theradius of the bleaching zone but the additional radial length of arm 18is not essential.

In actual operation, pulp wetted with bleach liquid and heated to thedesired temperature enters column 10 via entrance'opening 24. Thebleaching of the pulp is carried out in bleaching zone 10:: of column10, and the design of column 10 is such that the pulp and bleachingliquid are retained within bleaching zone 10a for a predetermined periodof time. The length of the bleaching period is varied by changing thelevel of the top surface of the stock in tower 10, i. c., longer bleachperiods areobtained by raising the stock level. As the pulp progressesdownwardly through the column, the weight of the pulp being fed into thebleaching chamber brings free bleaching liquid to the surface of thepulp, thus efiiecting a redistribution of liquid and adequate bleachingaction. Due to the compressive action resulting from the pulp being. fedinto the bleach tower, the pulp tends to mold itself into a shapesimilar to the contours of the column. Consequently, withdrawal of thepulp from the pulp to be moved outward over the periphery of bafile 14by the action of rotating jets 1.6, which slice and convey by hydraulicaction the major portion of the pulp outward over the periphery ofbafile 14. At times some segments of the pulp are not moved outwardly bythe action of jets 16, and when this occurs the weight of the pulp inbleaching zone 10a is concentrated on one or more of these smallsegments. This concentration of pressure forms dense, hard piers whichare substantially immune to subsequent jet action. Consequently, partialor complete stoppage of movement of stock down the tower results. Slicearms 18 follow jets 16, and they cut or slice the piers. and render thepulp of which they are composed susceptible to outward movement by theensuing sweep of jets 16. Jets 16 are rotated by a variable speed drive,and by controlling the speed of rotation of the jets it is possible tocontrol the rate of withdrawal of bleached pulp from tower 10. Also,uniform passage of bleached pulp from the bleaching zone to theslurrying zone of tower 10 can be effected without any formation ofpiers or pillars. Slurrying water is introduced to zone 10b via line 26and bleached pulp slurried in water is removed from the column via line28. The resulting slurry of bleached pulp in water is removed for anyfurther treatment that is necessary, and in some instances, dependingupon the nature and design of the equipment employed, it is desirable torecycle a small portion of the slurry to the column via line 30. Formost effective operation, the recycled slurry enters the bulged sectionof column 12 immediately above baffle plate 14. Water for jets 16 entersthe column via inlet 32. It will be understood that the water from jets16 provides a minor portion of the slurrying liquid for use in zone 10b.

Fig. 2 is a plan view through section 2--2 of the im proved bleachingtower showing jets 16 and slice arms 18 and their location in bleachingcolumn 10. Any number of jets and slice arms can'be employed to assistin the disintegration of piers of bleached pulp. It has been found,however, that two jets and two slice arms will effectively carry out theuniform movement of stock from zone 10a to zone 10b. It has also beenfound to be quite effective to employ the jets and slice arms in thesame horizontal plane, although this design is not essential for theoperation of the column; It is also desirable to place the slice arms atthe mid-point between baffle plate 14 and the lower extremity ofbleaching zone itla. in order to assist in the removal of the bleachedpulp from the bulged section of the column, it is desirable that slicearms 18 curve backwardly and away from any pillars that are to bedisintegrated by the slice arms.

Variations in the design of the bleach tower within the scope of thisinvention will be apparent to those'skilled in the art from the abovedisclosure. For example, in the above detailed description of theapparatus a column for bleaching pulp has been described. However, itwill be understood that a column or tower within the scope ofthisinvention can be used for other treating operations, such as an alkalineextraction treatment of bleached pulp. Also, the column has beendescribed as being cylindrically shaped, but this preferred design isnot essential to the operation of the column. For example, the design ofthe column can be such that a horizontal cross-section of the column isoval or square instead of circular as in a cylindrical column.

What we claim and desire to protect by Letters Patent is:

1. Apparatus for treating pulp comprising, in combination, an elongated,vertically disposed treating chamber; and, disposed below said treatingchamber and in direct communication therewith, a second chamber ofgreater cross-sectional area than said treating chamberand housing asolid baffle of greater cross-sectional area than said treating chamberand forming an annular space with the periphery of said second chamber;and means for moving treated pulp toward the periphery of said secondchamber.

2. Apparatus for bleaching pulp comprising, in combination, anelongated, cylindrically shaped, vertically disposed bleaching chamber;a second cylindrical chamber of greater diameter than said bleachingchamber disposed below and in direct communication with said bleachingchamber; a solid, circular baffle of greater diameter than saidbleaching chamber disposed in said second chamber and sloping downwardlyfrom the center of said second chamber and forming an annular space withthe periphery of said second chamber; means for spraying a liquid underpressure from the center of said second chamber toward the peripherythereof and disposed above said baflle; and an arm revolvable about thecenter of said second chamber and disposed above said 3. Apparatus forbleaching pulp comprising, in combination, an elongated verticallydisposed chamber, said chamber including a high pulp densitycylindrically shaped bleaching zone and a low pulp density cylindricallyshaped slurrying zone, said bleaching zone and said slurrying zone beingjoined by a protuberant section of said chamber; a solid circular batheof greater diameter than said bleaching zone disposed in saidprotuberant section and sloping downwardly from the center of saidprotuberant section and forming an annular space with the peripherythereof, the lower extremity of said balfie being in said protuberantsection; means for rotatively jetting a liquid under pressure from thecenter of said protuberant section toward the periphery thereof anddisposed above said baflle; and an arm revolvable about the center ofsaid protuberant section and disposed above said baflle, the length ofsaid arm being at least equivalent to the radius of said bleaching zone.7

4. Apparatus for bleaching pulp comprising, in combination, anelongated, vertically disposed chamber, said chamber including a highpulp density cylindrically shaped bleaching zone and a low pulp densitycylindrically shaped slurrying zone, said bleaching zone and saidslurrying zone being joined by a protuberant section of said chamber,the upper portion of said protuberant section being cylindrically shapedand of greater diameter than said bleaching zone and the lower portionof said protuberant section being in the form of an inverted truncatedcone in direct communication with said upper portion and taperingdownwardly and inwardly toward.

said slurrying zone; a solid circular bafile of greater diameter thansaidbleaching zone disposed in said protuberant section and slopingdownwardly from the center of said protuberant section and forming anannular space with the periphery thereof, the lower extremity of saidbafflle being in said protuberant section; means for rotatively jettingwater under pressure from the center of said protuberant section towardthe periphery thereof and disposed above said bafile; and an armrevolvable about the center of said protuberant section and disposedabove said baffie, the length of said arm being equivalent to the radiusof said bleaching zone.

5. Apparatus for bleaching pulp comprising, in combination, anelongated, vertically disposed chamber, said chamber including a highpulp density cylindrically shaped bleaching zone and a low pulp densitycylindrically shaped slurrying zone, said bleaching zone and saidslnrrying zone being joined by a protuberant section of said chamber,the upper portion of said protuberant section being cylindrically shapedand of greater diameter than said bleaching zone and the lower portionof said protuberant section being in the form of an inverted truncatedcone in direct communication with said upper portion and taperingdownwardly and inwardly toward said slurrying zone; a solid circularbafiie of greater diameter than said bleaching zone disposed in saidprotuberant section and sloping downwardly from the center of saidprotuberant section and forming an annular space with the peripherythereof, the lower extremity of said bafile being in said protuberantsection; means for rotatively jetting water under pressure from thecenter of said protuberant section toward the periphery thereof anddisposed above said baffle and revolving about the center of saidprotuberant section; and an arm revolvable in the same horizontal planewith said Water spraying means, the length of said arm being equivalentto the radius of said bleaching zone.

References Cited in the file of this patent UNITED STATES PATENTS1,968,994 Davies Aug. 7, 1934 2,513,344 McEwen July 4, 1950 FOREIGNPATENTS 904,673 France Mar. 12, 1945

1. APPARATUS FOR TREATING PULP COMPRISING, IN COMBINATION, AN ELONGATED,VERTICALLY DISPOSED TREATING CHAMBER; AND DISPOSED BELOW SAID TREATINGCHAMBER AND IN DIRECT COMMUNICATION THEREWITH, A SECOND CHAMBER OFGREATER CROSS-SECTIONAL AREA THAN SAID TREATING CHAMBER AND HOUSING ASOLID BAFFLE OF GREATER CROSS-SECTIONAL AREA THAN SAID TREATING CHAMBERAND FORMING AN ANNULAR SPACE WITH THE PERIPHERY OF SAID SECOND CHAMBER;AND MEANS FOR MOVING TREATED PULP TOWARD THE PERIPHERY OF SAID SECONDCHAMBER.